1. Field
The present disclosure relates to devices that communicate signals via capacitive coupling. More specifically, the present disclosure relates to devices that include connectors with features that enhance capacitive coupling with corresponding connectors on other devices.
2. Related Art
As integrated-circuit (IC) technology continues to scale to smaller critical dimensions, it is increasingly difficult for existing inter-chip connections to provide desired characteristics, such as: high bandwidth, low power, reliability and low cost. Several technologies have been proposed to address this problem, including proximity communication or PxC (for example, using capacitive inter-chip pads or connectors).
A PxC communication system based on capacitive inter-chip connectors provides dense inter-chip connections, with a pitch between neighboring connectors on the order of 10-100 μm. However, the capacitive coupling of AC signals between the inter-chip connectors, and thus the performance of a PxC communication system (such as the signal-to-noise ratio and bit-error rate), are sensitive to changes in the capacitance between the inter-chip connectors. This capacitance is small, and decreases as the spacing between the inter-chip connectors increases. For example, in a PxC communication system with a connector area of 106×106 μm2, a connector pitch of 106 μm and a capacitance of 500 fF, the bit-error rate is estimated to increase by a factor of 1020 as the spacing between the inter-chip connectors increases from 7 to 12 μm.
In contrast, the capacitive coupling of AC signals can be increased, and the performance of the PxC communication system can be improved, if the capacitance of the inter-chip connectors is increased. For example, the capacitance can be increased by increasing the connector sizes. However, larger connector sizes reduce the density of inter-chip connections, which is one of the advantages of PxC communication. Furthermore, as critical dimensions are scaled in semiconductor technology, the connector size is reduced. Because it is difficult to decrease the spacing between the inter-chip connectors, it may therefore be difficult to maintain the ratio of the connector area to the spacing between connectors on neighboring chips, which typically results in smaller capacitance, with a commensurate decrease in performance.
Hence, what is needed are devices with inter-chip connectors for use in PxC communication without the problems described above.